1. Technical Field of the Invention
The present invention relates to an electromagnetic connecting device for use with high voltages and large currents, which is detachable without using contacts.
2. Description of the Prior Art
Conventionally, a tandem press or transfer press is used to manufacture 3-dimensionally formed components with rather complicated shapes, such as automobile bodies or door panels. However, there are some pressed shapes that cannot be easily pressed using a conventional tandem or transfer press.
For instance, when a component, some part of which has a complicated shape, e.g. the handle portion of a door panel is pressed and formed, the edge cannot be formed precisely even with a pressing process, and the shape cannot be accurately finished. Therefore, when a high quality is particularly required, 2 or 3 processes are required, and as a result, a plurality of sets of upper and lower dies are needed, and a plurality of pressing processes must be provided, so that the production efficiency is low and the cost is high, which are practical problems.
In addition, there is a demand for aluminum material to be used to reduce the weight of a vehicle, however compared to steel sheets, aluminum has a large spring-back characteristic, therefore the shape cannot be finished precisely which is another problem in practice.
To solve these problems, the inventor of the present invention invented a continuous pressing equipment with which an aluminum material can be processed into a prescribed complicated shape using a small number of press machines, avoiding the spring-back phenomenon, and applied for a patent for it (Japanese patent application No. 65265/2000, not published at present).
This continuous pressing equipment is a tandem press or a transfer press with a plurality of press machines, using an electromagnetic forming apparatus provided within at least one press machine or between pressing machines.
According to the configuration of the present invention, because an electromagnetic forming apparatus is provided in a tandem press or transfer press or between presses, the material to be worked (panel) can be manufactured by electromagnetic forming (EMF) in conjunction with conventional mechanical pressing or hydraulic pressing. According to this EMF method, even a complicated shape can be formed because of the high-speed forming capability, and an aluminum material can be formed without any spring-back, which are advantages together with other preferred characteristics, so by using this method, even a shape that could not be formed by a conventional method can be formed.
The aforementioned electromagnetic forming apparatus is composed of an electromagnetic forming coil embedded in a die, a power supply unit, a switching circuit, etc. which must be connected electrically to this coil. However the power unit and switching circuit are so large that they must be installed at a fixed location outside the press machine, so a connector that connects the coil to the power supply unit that can be electrically detached is indispensable.
In an electromagnetic forming process, the coil must be excited with a large current (e.g. 100 KA or more) at a high-voltage (for instance, 10 kV), and a high-frequency (e.g., 30 kHz or more) half sine wave pulses.
However, in a conventional connector, the conductors (bus bars etc.) are held in contact by mechanical forces such as by applying a tightening torque, so a problem of such a connector is that excessive time and labor are spent in mounting and removing bolts etc.
Also with a conventional connector that is detachable without loosening bolts, known in the prior art, there is a large loss in the connector due to the large current and the contact resistance, so this type of connector has the problem that the above-mentioned high-voltage, large-current pulses cannot be transmitted efficiently.
The contactless power supply technology used conventionally in power supply systems of logistics etc. is restricted to a narrow range of applicable frequencies (about 20 kHz) and a low-voltage range, therefore the technology cannot be applied to the high-voltage, large-current pulses with a half sine wave shape at 30 kHz or more, that is, the object of the present invention.
Furthermore, the high-voltage, large-current pulse transformer that transmits electric energy through the electromagnetic coupling cannot be dismantled because the primary and secondary circuits are fixed.
The present invention is aimed at solving the aforementioned problems. That is, an object of the present invention is to provide a connector that can efficiently transmit high-voltage (for example, 10 kV), large-current (for instance, 100 kA or more) current pulses with a narrow pulse width (e.g., 30 xcexcsec or less) and can be easily disconnected.
The present invention offers an electromagnetic connectors for high voltages and currents, comprised of a primary winding (12) connected to a high-voltage, large-current power supply (1), a secondary winding (14) connected to an electromagnetic forming coil (2), and a magnetic core (16) for passing the magnetic flux produced by the primary winding to the secondary winding, in which the magnetic core (16) is comprised of a primary core (16a) on which the primary winding is installed and a secondary core (16b) on which the secondary winding is installed; the primary core and the secondary core are magnetically connected together by putting them in contact or in close proximity, and separated each other when the connector is disconnected.
According to the configuration of the present invention, the primary core (16a) and the secondary core (16b) are in contact or closely located, and are therefore connected magnetically; the magnetic flux produced by the primary winding using power supplied from the high-voltage, large-current power supply (1) passes through the secondary winding (14) in which the flux induces high-voltage, large-current pulses that are applied to the electromagnetic forming coil (2) for electromagnetically forming the workpiece. In addition, because of the magnetic connection between the primary and secondary cores, high-voltage (for instance, 10 kV), large-current (for example, 100 kA or more) narrow pulse-width (e.g., 30 xcexcsec or less) current pulses with a half sine wave shape can be transmitted efficiently.
Generally speaking, a conventional direct connection for very-high-voltage, large-current pulses to transmit electrical energy needs a large-scale configuration; however, the present invention uses an electromagnetic coupling instead of the conventional direct connection, and provides an easily detachable connector that can withstand a high voltage and has no contact resistance, that can be used when a power supply and a load must be frequently disconnected and re-connected. Thus, an apparatus using large-current pulses at a very-high voltage can be easily assembled into a production line where a time interval is a problem.
According to a preferred embodiment of the present invention, the above-mentioned magnetic core (16) is shaped as a closed rectangle, and the aforementioned primary core (16a) and secondary core (16b) are U-shaped, formed by cutting the above-mentioned rectangle into two parts.
Using this configuration, a detachable magnetic core (16) can be easily formed, and the leakage of magnetic flux, when the cores are connected, can be made small.
In addition, the two parts cut as above can be in close contact with each other or located close to each other when connected, and can be configured to keep a space between them when they are disconnected.
In this configuration, the large-current, high-voltage power supply can be easily connected or disconnected in a contactless manner by only placing the cut surfaces in contact (or close together) or separating them, respectively.
Furthermore, it is preferred that the primary winding (12) and the secondary winding (14) are wound on each core in such a way that the windings overlap each other concentrically when the cores are connected.
This configuration can pass the magnetic flux produced by the primary winding, through the secondary winding, with minimum leakage of magnetic flux when the cores are connected so improving the efficiency of the coupling.
The above-mentioned magnetic core (16) is preferably made of silicon steel sheet, ferrite material or amorphous material.
The core is not limited only to ordinary silicon sheet steel, and the use of a ferrite material or amorphous material can increase the coupling efficiency.
The aforementioned primary winding (12) and secondary winding (14) are molded in a plastic resin, separately.
The above-mentioned configuration can suppress the vibration of the windings due to large currents, while ensuring that the windings are capable of withstanding high voltage.
Other objects and advantages of the present invention are described below referring to the attached drawings.